Compression ignition does not require a specific mixture in the combustion chamber because each fuel droplet ignites independently. There is no dependence on the reaction traveling from the spark plug through a mixture that is rich enough to allow it to sustain. Therefore the diesel engine has no throttle, as noted, and excess air does not react.
Airborne_Again wrote:
Diesels are always fuel-injected
Oh, wow, you are right! The “second prototype” by Rudolf Diesel was fitted with “air-blast injection” in… January 1894. That technology is as old as 1890. I had no idea fuel injection was so old.
https://en.wikipedia.org/wiki/Diesel_engine#The_first_diesel_engine
https://en.wikipedia.org/wiki/Air-blast_injection#History
From the above mentioned book (I’ve just reached the end of WW2):
I don’t get it. According to that video the swirl throttle is one way of controlling a compressor (to some degree). Lots of jet engines have exactly the same thing, only they call it variable inlet vanes. All that is done is to reduce the work done by the compressor, by (indirectly) lowering the outlet pressure. In a turbojet this enables faster spool up of the engine, faster throttle response. You are still throttling the flow though. The difference is that with a normal throttle this is done by restricting the flow, whereas this swirl throttle (as inlet vanes) does it by implying spin on the flow. Variable inlet vanes has an additional feature. They will also enable correcting the flow at less than optimal operation points. This happens when varying speed (of the aircraft and engine) and when changing the density.
A spark ignited engine must be able to throttle the air, or the mixture will be all wrong (too lean at low power). A compressor in front will not change this, but I guess by modulating the compressor, this can be done. A swirl throttle is perhaps a better way to do it than a normal throttle? A turbo can have the throttle either in front or aft of the turbo. Don’t know what difference it would make in practice, but carboreted setup typically has the throttle in front for obvious reasons.
Another thing with that video is the compressor itself. It has 100% radial vanes, also at the inlet. This is a very, very crude design. So crude in fact, it’s hard to believe a German engineer would ever produce such a thing regardless of time period 
It leads to high swirling flow at the inlet, basically throttling the flow from the start. A swirl throttle would correct this to some extent I guess? It’s hard to imagine the compressor would work at all in any satisfactory fashion without such a device.
To me, a swirl throttle could improve performance of a poor compressor design. But with a good (normal) compressor design, will it make any practical difference in a setting like this? I’m not convinced.
